| Title | Coil Tubing Acid Stimulation: The Case of Awi 8-7 Production Well in Salak Geothermal Production Field, Indonesia |
|---|---|
| Authors | Riza G. Pasikki, Todd G. Gilmore |
| Year | 2006 |
| Conference | Stanford Geothermal Workshop |
| Keywords | acid stimulation, coil tubing, formation damage, awi 8-7, skin, sandstone acid, non-isothermal reservoir |
| Abstract | Awi 8-7 is a new well drilled in the Salak geothermal field during 2004. Despite promising indications, the initial steam flow rate from this well was below expectations. A completion test that consisted of a pressure-temperature-spinner (PTS) survey, an injectivity test, and a pressure fall-off (PFO) test was conducted to diagnose the problem and to characterize the initial state of individual permeable zones. Injectivity and pressure fall-off tests indicated that Awi 8-7 had a low injectivity index (II) and a positive skin. These data and the fact that the well lost about 94,500 bbls of water-based mud during the drilling process suggested the presence of near-wellbore formation damage. An acid stimulation treatment was designed and carried out to improve well performance. The treatment used a hydrofluoric acid system known as Sandstone Acid that was placed at the target zones via two-inch coiled tubing. Post-acidizing well test analysis demonstrated that the acid stimulation successfully improved overall well characteristics. Total II increased from 2.56 to 6.55 kph/psi, permeability-thickness (kh) product increased from 252,000 to 403,000 md-ft, and the skin decreased from +2.2 to -1.2. A flow performance test after the acid job has confirmed a significant improvement of Awi 8-7 deliverability: maximum discharge pressure increased from 211 to 297 psig, while production output at a wellhead pressure of 150 psig increased from 70 to 160 kph of steam. |